Partialeq #206
Partialeq #206
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Signed-off-by: Alexandru Cihodaru <[email protected]>
Implement PartialEq for Error enum and update tests. Signed-off-by: Alexandru Cihodaru <[email protected]>
Implemented PartialEq for Error enum. Considering that from this file the only io error returned are OS error usage of raw_os_error offers anything that is needed. Updated tests to use PartialEq for error cases. Signed-off-by: Alexandru Cihodaru <[email protected]>
Derive PartialEq and update tests to check for equality on error cases. Signed-off-by: Alexandru Cihodaru <[email protected]>
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| }, | ||
| ) => left_expected == right_expected && left_completed == right_completed, | ||
| (Error::IOError(left), Error::IOError(right)) => { | ||
| // error.kind should be enough to assert equallity because each error |
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While this is true, it does not mean that kind can be used to compare errors. The reason why io::Error does not have PartialEq implemented is because it cannot be implemented truthfully. The first example that comes to mind is NotFound. A not found error thrown for file1 is not equal to an error thrown for file2. This is one of the reasons why we cannot actually compare the io::Error like that because it has other metadata that is specific to the error type. We can say instead that we are willing to accept the loss of information in comparing errors because vm-memory errors are widely used in other crates as well and it is very limiting to not have PartialEq implemented.
| @@ -73,6 +73,33 @@ pub enum Error { | |||
| HostAddressNotAvailable, | |||
| } | |||
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| impl PartialEq for Error { | |||
| fn eq(&self, other: &Self) -> bool { | |||
| match (self, other) { | |||
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One reason I don't particularly like these kinds of implementations for PartialEq is that it will silently fail when you add a new error type if you don't explicitly add it in the below match as well. I would propose we add a test that just fails when a new variant is added and has a comment something like: "If this failed it means you added a new error type. Make sure you also add that to the PartialEq implementation. Once you've done that feel free to fix this test". This will serve as a warning when adding new types. I am also open to other ideas as this is rather dummy 😆
Summary of the PR
Implement PartialEq for Error enums.
Fixes: #194
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